Gasifier help?

[Gagster]

If anybody has practical experience experimenting with gasifiers, I could use some help.  My first attempt at a gasifier is a simple updraft batch unit.  It consists of a 5 gallon stainless keg with the top cut off.  The keg is about 10 inches diameter and about 30 inches deep.  There's a grate near the bottom so ash can settle out.  A 1/2" id pipe comes in under the grate with a 45 degree elbow deflecting the inlet downward to keep ash out of it.  The keg is inside of a 30 gallon galvanized trash can with fiberglass insulation stuffed between the two.

I lit a wax/sawdust fire starter and placed it on the grate.  Next I dumped in some charcoal I made using the old "pain can in the fireplace" trick.  When the flames went out and it was good and hot I added miscellaneous fuel including plywood and pine quarter-round scraps from an earlier project, some sticks from around the yard, some wood chunks, and other goodies I had on hand.

At this point, all I'm getting is smoke.  I can't ignite the gas that is coming out of the gasifier at all.  I've played with opening and closing the ball valve on the air inlet pipe and it doesn't seem to make any difference.

Any help would be greatly appreciated.

Thanks in advance!

Gagster

[Nando]

Maybe better if you subscribe to a WOODGAS group

WoodGas@yahoogroups.com

send a message placing: subscribe ;in the subject line and in the body of the message

Nando

[WXYZCIENCE]

Nando, I have been looking for just such info myself. Searched it on this board. Found lots of links to gasifier. They fits perfectly within this forum. I want to power a small electric genny with the gas and use the excess heat for a green house.


Click on 'search the board' you will find lots of info. Joseph  

[thefinis]

It needs a real hot fire bed. Pull air through the unit and use as small an opening in grate area as possible to create a hot jet. Your unit may just have needed to run opened with your wood in it till it reached operating temp then stir/shake it and shut it. let it vent for a few minutes and then try the resulting gases. Your unit seems small in wood storage area. The wood needs to char and if there is too much moisture you end up diluting the already poor mixture. Small dry chunks 2x2x2 aprox, a hot fire, a bigger bin and pull air through would be my advice. I don't recall the sizings on the unit for the amount of draw wanted.

You don't say anything about the lid or how you shut the unit up or what size pipe you are drawing through. You need it closed up tight if it isn't. It is a wood cooker. Remember carbon monoxide is a poor fuel and a sneaky poision gas. Wood gas is a poor mix at best. It is diluted with nitrogen co2 steam and any air leaks. It can be improved by cooling gas to condensation point and airtight construction.

It has been years and years since I played with this and I gave up on it. I think I still have Mother E's original blueprint/plans here somewhere. It is too high an energy user on gathering and sizing the fuel unless you have a ready made source. If you want to use bigger size fuel build a much bigger unit like a 30-40 gal waterheater and expect to have to shake and stir it.

Finis

[Gagster]

Ah!  Egg-celent!  That's some good info, Fin.  I don't know if you're familiar with the five gallon sanke kegs, but basically it's a heavy duty thick-walled stainless construction with an inch and a half diameter port in the top where the valve sits.  I cut the top off just below the shoulder of the keg with a die grinder and removed the valve.

When I had my fire burning (smoldering, more like) I had the top of the keg placed back on the rest of the cylinder and the seam wrapped with aluminum tape.  It wasn't exactly air tight, but pretty decent.  The exhaust was very smoky so it was easy to see and it was nearly all coming through the port at the top.  I didn't have a fan to induce a draft so it was just the convective action pushing the gas out the top.  That should make it more of a positive presure system if not neutral.  The leaks, if anything, should have just lost me some product rather than diluting what I got.

So, things I've learned from this:

I need to use smaller fuel

I will have to find a way to induce a draft

rather than just try to use the producer gas out of the port at the top, I should close that port off and actually pipe the gas to a water bath to cool it as a purifying step

This should keep me busy tomorrow.  

BTW, I do have an old water heater that I just got from someone.  I was planning to use it as a hot water storage tank for a solar collector and maybe for salvaging heat from the gasifier.  It would be something of a shame if I had to kill the water heater to build a bigger gasifier, but if that's what it takes...

Thanks for the tips.  This really helped me out!

Gagster

[RogerAS]

Hey,

Do a google search for the FEMA plans. This is a different tpe of gasifier (downdraft) that has DETAIL in both words and picts to show how. I downloaded it and had wife print out at work. In that design a small blower motor was used to get the thing up to speed before even attempting to light the engine. I think your current cooker could be used with the other design. Hope this helps. If u can't find the thing I have the PDF and could send as email attachment. It's too big to put in my personal files, but it's public domain info, so that's not an issue.

[thefinis]

Okay the old brain is finally kicking in plus I pulled out all of my old papers and did some quick checking to see if there are any new updates on the internet. What are you going to use the woodgas for? I did not catch what a difference an updraft model would make as I forgot that all the smoke must be drawn though the burning char and cracked. I hate to say it but I don't think an updraft model will work. Mine was downdraft but I never got around to hooking it up to a motor. it worked but I decided that by the time I added up harvesting, hauling, processing/sizing and drying the wood I could just use all that time/fuel to buy gasoline for the truck.

Usually draft is induced as it is drawn into motor. The hot flame jet at the grate is what cooks the rest of the wood above it. It is usually regulated by the draw. No draw and the flame dies to a smolder more draw and it starts carving a chamber in the char. This chamber/bridging effect is part of why it needs stirring or shaking and one of the reasons why wood size is important.

Flame jet is misleading as you are burning char in an oxygen deprived atmos. A red hot superheated pillar area of char is more accruate. It cracks the co2 and h2o into co and h2 as the char is consumed in an o2 starved atmos. There are other gases released by the charing wood but you usually try to burn these in the cracking zone. The flame jet is very high temp but as it carves out a chamber it diffuses making a lower temp over a larger area. As the temp drops its ability to crack the gases does too. Meaning you will get a higher ratio of co2 and steam. Excess moisture causes this too.

I could go into the need for air nozzels etc but I think I am going to second Nando and say try a visit to WoodGas@yahoogroups.com   It is one of those things like deciding to build a pm alt you have the right idea but now you need to know rpms mag/wire sizes and coil turns.

Here is a page with something like you have started but downdraft. The rest of the article can be found through the link at the bottom of the page.

http://www.windward.org/notes/notes63/wal63_b.htm

I have lots of info in the files if I can help.

Finis

[wdyasq]

I agree, why reinvent the wheel.

Google search - fema woodgas filetype:pdf

First hit: http://www.rebelarmy.com/rebenergy.pdf

I'm sure it is on 40 other sites too.

Ron

[Gagster]

Okay, after all the comments (including Nando's to check out the yahoo group) I've decided that there is nothing for it but to convert my burner to a downdraft model.

The materials:

I had an 80mm PC case fan lying around.  I dug up a 12V wall wart power supply.  I took a trip to Menards for ideas and came up with a 2" to 1 1/4" galvanized pipe reducer.  I like to homebrew beer and wine.  One of the things I had laying around was a 5gal pail with a gasket sealed lid and a hole for an airlock.  It was originally used for shipping frozen grapes.

The conversion:

I took a 1.5 inch hole saw and ran it through where the airlock hole was.  This gave me a good port under which to mount the fan.  I cut a small hole for the case fan's power connector and mounted that in the lid.  Some 600 degree gasket sealant (the blue stuff) seals off the holes, and is what I've used as an adhesive to mount the fan to the underside of the lid.  I  soldered a female connector to the leads of the wall wart so that I could plug and unplug the fan from outside the bucket.  On the top of the lid I used the blue goo to glue (Nice rhymes, eh?) the reducer to the lid over the fan port.

My first pass at a burner had a 1/2" galvanized pipe through the outer shell and into the bottom of the burner chamber with a 45 degree fitting inside to deflect the incoming air charge down and avoid ash in the inlet.  The bucket is now an airtight plenum with a draft fan and small chimney.  Tomorrow I will cut a port in the bucket, insert the pipe from the burner into the hole, and blue goo it.  Once the goo cures, I can fire the burner again with the draft fan and run it in a downdraft configuration.  If all goes well, I should get a nice "olympic torch" above the reducer.

I'll get some pics tomorrow and post them in my gallery so that all this will actually make sense.

[Gagster]

Okay.  I've gotten some pics.  They're up at http://gallery.halfront.com/Gasifier.  The pics show the burner and plenum.  The only part you can't really see in the pictures is the 80mm PC case fan that is mounted to the inside of the plenum lid.

[Gagster]

Doh!  Hit submit too soon.  I mean to add that while I've got a decent draft going, the exhaust is decidedly not flammable.  I'm trying to light the exhaust with a propate torch so I know I should have plenty of ignition heat.

The cylinder in the burner is getting awful hot so I'm doing better than yesterday.  Still don't know what's gone wrong, though.  Still not enough draft?  Fuel size too big?  My fuel is wood chips that they sell in a bag for use with a backyard smoker.  It seems like a bit of a waste, but I needed fuel and I'm impatient.    Sizes of the wood chunks range from the size of a cigarette lighter to a bit smaller than my fist.

Any thoughts?

(I'll cross post to the yahoo group just to be sure.)

[thefinis]

How long did you let it run before trying to light gas? Is that a water bath in the plastic bucket? What does the smoke smell like it should have an off funky smell. Kind of like old cresote in a stove pipe or a barbque pit when you fire it up with wood and then shut down the lid when it first flames too high.

It might be worth while to try it with just a bag/load of charcoal and see if it will make a flame. Most of the units I have seen tend to be bigger except for the charcoal ones. My guess is that you still aren't getting a hot enough bed of char maybe from pulling too much moisture through keeping temps down.

I still have the question of what you want to use gas for. In a motor it needs to be real clean no tars ie downdraft but for an open flame/boiler the tars actually add btus so updraft might work. Did find drawings of some updraft models but main drawback is tars in the gas stream making it unsuitable for anything but open flame without huge amounts of tar removal plus it makes more pollution.

Finis

[Gog]

I'm a bit late but have a look here

http://www.fluidynenz.250x.com/

The anniversary gasifier project has a good pdf drawing attached

[gale]

Farm show magazine for December vol 30 no.6, 2006.  Has a article about a man who has built two pick-ups to operate on bio gas.  Interesting read, they have internet acess to certain articles on their cover.  Currently they do not have access to this issue, only last monthes issue, but hopefully in a few days they will also have this issue. http://www.farmshow.com/

[jaybee]

The original poster mentioned batch production of wood gas. If it is just for heating then an inverted downdraught gasifier will produce an immediate flame above the wood.

I have built one myself - http://the-goodlife.blogspot.com/search/label/wood%20gas